1. Field of the Invention
The present invention relates to a liquid ejection head for ejecting liquid and a method of manufacturing the same.
2. Description of the Related Art
An ink jet printing method disclosed in Japanese Patent Application Laid-Open No. S54-51837 is a method in which liquid is ejected by causing thermal energy, which is the driving force for liquid droplet ejection, to act on the liquid. More specifically, in the ink jet printing method, liquid acted on by thermal energy develops air bubbles as the liquid is vaporized by being heated. By expansive force which accompanies the growth of air bubbles, a liquid droplet is ejected onto a print medium from an ejection orifice. Such liquid droplets cause predetermined image information such as characters or an image to be printed on the print medium. A print head used in this method includes, for example, the following:
(1) an ejection orifice for ejecting liquid therefrom;
(2) a liquid chamber communicated with the ejection orifice for supplying the liquid for ejecting;
(3) a heat storing layer for storing heat generated by the ejection energy generating element;
(4) an ejection energy generating element for generating thermal energy for causing a liquid droplet to be ejected from the ejection orifice; and
(5) a passivation layer for protecting the ejection energy generating element against the liquid.
Further, Japanese Patent Application Laid-Open No. H09-011479 discloses a method in which an ink supply port communicated with the above-mentioned liquid chamber for supplying liquid to the liquid chamber is formed by anisotropic etching. Further, Japanese Patent Application Laid-Open No. H10-181032 discloses a method in which a sacrificial layer is used to form the ink supply port with high precision. Still further, Japanese Patent Application Laid-Open No. 2005-035281 discloses a method in which a process of forming the sacrificial layer is simplified.
In the methods in which the ink supply port is formed as described in the above-mentioned documents, crystal anisotropic etching of an Si substrate having a <100> surface orientation with an alkaline solution is used. This utilizes difference in the rate of dissolving in an alkaline solution depending on the surface orientation. More specifically, the etching progresses so as to leave a <111> surface having an extremely low rate of dissolving.
Here, the ink supply port formed by crystal anisotropic etching has a structure in which an exposed silicon surface is in direct contact with ink. In recent years, as print quality of ink jet printers is improved, materials having various concentrations and materials which are strongly alkaline of pH 7 or higher have become more frequently used. Then, ink in contact with a silicon portion may dissolve the silicon. Therefore, it is desired to protect with an ink-resistant member the ink supply port which is in direct contact with ink. For example, Japanese Patent Application Laid-Open No. 2006-315191 discloses a method in which a protective layer is formed by forming an inorganic film on the ink supply port and on a part of an ink flow path.
Study by the present inventors reveals that, in the method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2006-315191, coverage may be insufficient, because an inorganic film is formed on the ink supply port by sputtering. Further, large-scale facilities such as film formation equipment and large-scale processes are required, and thus, the costs may increase.